1. Field of the Invention
The present invention relates to a toner used in a copier or a printer performing image formation by a form of electrophotography or ionography, and to an image formation apparatus employing the toner. In particular, the present invention relates to a color toner for optical fixing containing a novel infrared light absorbent which absorbs optical energy and converts it into heat, and is fixed onto a recording medium such as a recording paper through optical irradiation thereof, and an image formation apparatus employing this toner.
Moreover, in other words, the present invention relates to a toner by which possible disorder of the color tone of the toner occurring as a result of the toner containing an infrared light absorbent as a component thereof is controlled, and a bright color tone also can be obtained even for a hue which is easy to be influenced of muddiness, such as lemon yellow, and an image formation apparatus employing this toner.
2. Description of the Related Art
As an image formation apparatus which performs printing of documents, copying, etc. in an office etc., one which employs electrophotography or ionography as a drawing principle is used regularly.
In an electrophotographic system, a uniform electrostatic charge is given on a photoconductive insulator (photosensitive drum, etc.), and an electrostatic latent image is formed by applying an optical image on the photoconductive insulator by any of various methods. Subsequently, development of this electrostatic latent image is carried out so as to visualize it using fine powders called toner, then, after transferring the thus-obtained toner powder image onto a recording medium, such as a paper, it is fixed thereonto, and, thus, a printed image is obtained.
On the other hand, in an ionographic system, ion (charged particle) is generated by an ion generating unit, using a carrying drum which has an electrostatic coating as a dielectric member for carrying electrostatic charge, by using the ion, an electrostatic charge image is formed on the surface of the dielectric member. Then, the thus-formed electrostatic charge image is developed by a toner, and a printed image is obtained through processes of transferring and fixing like those of the above-mentioned electrophotographic system.
For the above-mentioned two image forming systems, the fixing process is approximately the same therebetween. A toner powder image formed on the recording medium is fused by pressurization, heating, solvent steam, light, etc., and thus, adheres/is fixed onto the recording medium.
Recently, for the fixing process, an optical fixing form by which a powerful light is applied at a toner powder image and fuses the toner attracts attention by the following reasons:
(1) Since this is non-contacting fixing, blurring of an image, dust, etc. do not occur in the fixing process, and the resolution is not degraded.
(2) There is no waiting time after turning on of a power supply in the apparatus, and, thus, a quick start is possible.
(3) Since an exothermic unit, such as a heating roller, is not used, even if a recording paper is blocked in the fixing assembly by the system failure, there is no problem of ignition.
(4) Even for paper with paste, pre-printed paper, paper having different thickness, and so forth, it is possible to perform the fixing process regardless of such quality of the material and thickness of recording medium.
Currently, for this optical fixing system, the most general method is a flash fixing method which uses a xenon flash lamp for the light source therefor.
Process in which a toner is fixed to a recording paper in the above-mentioned flash fixing method will now be described. A toner (powder) image is transferred from a photosensitive drum etc. onto a recording medium (simply referred to as a recording paper, hereinafter). At this time, as the toner merely adheres to the recording paper in a form of a powder image, when it is rubbed by a finger, for example, the image is easily destroyed.
When flash light (glint of light), such as a xenon flash, is applied to this toner powder image, the toner absorbs the optical energy of the glint of light, this increases in temperature and softens, and thereby, sticks to the recording paper. Then, when the temperature is lowered after the glint-of-light application, the toner image solidifies, and, thus, a fixed image is obtained. It is important to prevent so-called poor fixing performance which causes degradation of quality of the image as a result of the once fixed image being exfoliating from the recording paper when it is bent, or rubbed.
In order to prevent such a situation, the toner used in the optical fixing should satisfy at least the following conditions simultaneously:
(1) The capability of the toner is improved so that the toner absorbs a sufficient quantity of heat.
(2) The toner should fuse promptly by absorbing heat, and permeates a recording paper.
(3) After being cooled, the toner should adhere to the recording paper firmly.
Moreover, as shown in FIG. 1, a xenon flash lamp generally used by the optical fixing method has a luminescence distribution through a wider range from ultraviolet to infrared wavelength zones. Especially, this has a strong luminescence intensity, in a near-infrared zone of 800 through 1050 nm. In order to achieve a toner having superior fixing performance, establishment of technology, i.e., technology of using optical energy of this near-infrared zone efficiently, that is, effectively reduction of necessary optical energy to be used, is also needed.
A demand for color printing is increasing especially in recent years. Although a colorant used for a color toner absorbs light in part of a visible light wavelength zone, the light absorbing efficiency for a near-infrared wavelength zone is low. That is, the colorant used for a color toner has a characteristic of being hardly absorbing thermal energy from applied light, and, thus, the toner needs a large energy to be applied for fusion thereof.
Therefore, to put into practice a color toner by which satisfactory fixing performance/characteristic is obtained while the necessary energy can be reduced in the optical fixing system is demanded.
Moreover, with regard to a black toner, while a black color agent which is a colorant absorbs all light of the visible light zone, it also absorbs light of the near-infrared zone relatively well. Therefore, it has been already put in practical use in an electronic photography apparatus which employs the optical fixing system. However, in order to cope with an increasing demand for saving energy in recent years, reduction of the necessary optical energy to be applied is demanded. Thereby, further improvement of light absorbing efficiency of the black toner is demanded.
For the above-mentioned demand, various proposals have been given by Japanese Laid-Open Patent Applications Nos. 58-102247, 60-57858, 7-191492, 10-39535 and 11-65167, Japanese Patent Publication No. 7-23965, Japanese Patent No. 3011936, Japanese Laid-Open Patent Applications Nos. 2000-147824, 2000-214626, etc. By these proposals, technology which heightens flash light absorbing capability as a result of a toner containing as an infrared light absorbent, an amide compound which has a light absorbing capability for a near-infrared zone such as for example, aminium salts, a thiol nickel family complex, an indium oxide family metal oxide, a tin oxide family metal oxide, a zinc oxide family metal oxide, tin acid cadmium, a phthalocyanine and/or naphthalocyanine family compound, a merocyanine pigment, a polymethine pigment, a specific amide compound, etc.
Among the above-mentioned compounds, aminium salts, thiol nickel family complex, phthalocyanine and/or naphthalocyanine family compound and so forth are relatively excellent in performance balance as an infrared light absorbent to be added to a toner for the optical fixing process.
However, aminium salts have the problems as mentioned in the following items (1) and (3), and, also, the thiol nickel family complex and phthalocyanine and/or naphthalocyanine family compound have the problems as mentioned in the following items (2) and (3):
(1) The electrification of the toner may be problematically influenced thereby.
(2) When the toner has a color other than monochrome color, the color tone of the compound used as the infrared light absorbent therein may affect the hue of the toner.
(3) The unit price of the compound may cause the cost rise of the toner highly.
Therefore, an object the present invention is to provide a flash fixing toner at low cost by which influence on electrification performance and a hue change based on infrared light absorbent addition can be effectively reduced, and to provide a color image formation apparatus employing the toner.
In particular, an object of the present invention is to provide a toner by which muddiness of color tone resulting from adding the infrared light absorbent is suppressed, and which provides a bright color tone also for a hue such as lemon yellow which tends to produce muddiness, and to provide an image formation apparatus employing the toner.
A toner according to the present invention for optical fixing, includes, at least:
a binder resin;
a colorant; and
an infrared light absorbent,
wherein:
a coloring opacity of the infrared light absorbent is 20 or less; and
the infrared light absorbent has a structure expressed by the following chemical formula (1) and/or (2); 
wherein:
each of R1 through R8 denotes a substituent added to a benzene ring or a naphthalene ring, and comprises a hydrogen, a halogen atom, a saturated or unsaturated hydrocarbon group having the number of carbons in a range between 1 and 18, or an oxygen and/or nitrogen content hydrocarbon group having the number of carbons in a range between 1 and 13; and
M denotes two hydrogen atoms, a divalent metal, or a trivalent or tetravalent metal derivative.
Thereby, since the infrared light absorbent with a low coloring opacity is thus used, even when the color of toner is of a light hue, such as yellow, it is possible to form a bright/clear image without muddiness in color.
The infrared light absorbent may have a specific surface area in a range between 40.0 and 120.0 m2/g measured by a BET method.
Thereby, the infrared light absorbent in the state where it is added into the toner provides a function to transform the irradiated optical energy into thermal energy effectively.
The inventors and so forth confirmed that, in order to achieve the function in which the infrared light absorbent in the state where it is added to the toner transforms the irradiated optical energy into thermal energy effectively, in measurement of the phthalocyanine compound expressed by the above-mentioned chemical formula (1) and/or the naphthalocyanine compound expressed by the above-mentioned chemical formula (2) by the BET method, the specific surface area thereof should be not less than 40.0 m2/g, more preferably, in a range between 40.0 and 120.0 m2/g.
FIG. 2 shows a result of measurement of the specific surface area of the infrared light absorbent added to the toner and the calorific value measured when light was applied to the toner by using a photo-acoustic spectroscopic analysis (PAS: Photo-acoustic Spectroscopy). According to this analysis result, as the specific surface area of the infrared light absorbent increases, the light absorbing calorific value per the amount of addition of the above-mentioned phthalocyanine and/or naphthalocyanine compound increases.
The inventors etc. confirmed that the increase of the specific surface area (to produce finer particles) of the infrared light absorbent is far effective rather than increase of the amount of addition of the above-mentioned compound and so forth from a viewpoint of the light-to-heat conversion effect. The inventors and so forth inferred that the above-mentioned effect can be obtained not only because the light-receiving area thereof increases when the above-mentioned phthalocyanine and/or naphthalocyanine compound has finer particles, but also because the contact surface with the dispersion medium such as the binder resin increases thereby, and, as a result, heat conduction between the infrared light absorbent and the dispersion medium can be performed smoothly.
By the way, according to research by the inventors and so forth, in case where the toner is manufactured by a grinding method, when the specific surface area is made more than 120.0 m2/g, no improvement in light-to-heat conversion efficiency is found, but rather it tends to be degraded. Furthermore, grinding and making finer particles raises the manufacture cost. Therefore, to increase the specific surface area without limitation is not preferable.
The inventors etc. inferred, for the fact that there is a case where the light-to-heat conversion efficiency is degraded as the specific surface area is further increased as mentioned above, as follows:
FIG. 3 shows the rate of surface existence of the above-mentioned infrared light absorbent near the surface of particle of the toner (the depth of about 2 micrometers). This rate of surface existence is a value contrived as a result of ultimate analysis (SIMS) in which the central element M of the above-mentioned phthalocyanine and/or the naphthalocyanine compound used as the infrared light absorbent is regarded as the label substance.
As can be seen from the analysis result, the rate of surface existence of the above-mentioned compound near the surface of the toner particle is reduced as the specific surface area of this compound added internally into the toner increases. The maximum difference thereof reaches 6 times.
The optical energy applied to the toner particle only reaches the infrared light absorbent of the toner surface or the neighborhood thereof; and does not reach the infrared light absorbent in the central part of the particle. By this reason, the infrared light absorbent located in the center of the toner particle does not contribute to light-to-heat conversion efficiency very much. Therefore, the further increase of the specific surface area of the infrared light absorbent rather causes reduction in the surface existence rate of the compound near the toner particle surface although it results in slight increase in the light-to-heat conversion efficiency per unit weight. Thus, it is inferred that the saturation or reduction tendency of the light-to-heat conversion efficiency as total results from the influence of the above-mentioned reduction in the surface existence rate near the toner particle surface.
In addition, the mechanism in which the infrared light absorbent near the toner particle surface existence rate decreases as the particle of the infrared light absorbent is made finer can be inferred to relate to a fact that a toner lump tends to break at the interface between the toner internal additive and binder resin during a process of grinding to produce finer particles. That is, when the particle of internal additive material of the toner (the infrared light absorbent, etc.) is somewhat large, a big interface exists between binder resin and the additive in the toner. Since this part is weak to a shock, the toner lump breaks at the part. As a result, the toner internal additive material is easy to be exposed to the surface of the thus-generated toner particles. Accordingly, the toner particle surface existence rate of the toner internal additive material increases in comparison to that at the toner central part.
However, since the mechanical strength difference between part of only the binder resin and part having interface between the binder resin and the internal additive maternal in the toner becomes small in the toner lump when the particle size of the internal additive material in the toner becomes very smaller, the above-mentioned mechanism becomes not likely to occur in crush of the toner lump. And, the more the internal additive material has finer particles, the more the difference of the surface existence rate of the internal additive maternal particles between neighborhood of the toner particle surface and the inside thereof is reduced.
In addition, atomization of the infrared light absorbent reduces the coloring opacity of the above-mentioned phthalocyanine and/or the naphthalocyanine compound.
FIG. 2 also shows the specific surface area of the above-mentioned phthalocyanine and/or naphthalocyanine compound added to the toner and the coloring opacity of the toner which contains only this compound as the coloring component. From this analysis result, it can be seen that the coloring opacity per amount of addition of the compound falls as the particle size of the above-mentioned compound is made finer.
The definition and the measurement method of the coloring opacity will be described in detail later.
The central element M in the chemical formula (1) and/or (2) may comprise aluminum or tin.
When Al or Sn is thus used as the element M of the above-mentioned phthalocyanine and/or naphthalocyanine compound, it can become possible to reduce absorption of the visible light wavelength zone (to further lighten the color) while the main absorption wavelength zone is maintained in a range between 800 and 1000 nm. Thereby, it is possible to remarkably reduce the inference on the color tone of the toner in a case where the phthalocyanine and/or naphthalocyanine compound is added to the toner.
FIG. 4 shows change in absorbance of the visible light wavelength zone resulting from changing the central metal M of the above-mentioned phthalocyanine and/or naphthalocyanine compound.
Although the absorbing power in the infrared light wavelength zone is the order of vanadiumxe2x89xa7aluminumxe2x89xa7tin greater than titanium, it turns out that it is titanium greater than vanadium greater than tin greater than aluminum in the visible light wavelength zone. The fact that the absorption in the visible light wavelength zone is small shows that the original color tone of the toner is prevented from being spoiled even for a toner of light color tones, such as lemon yellow.
The fact that the absorption for the visible light wavelength zone is thus smaller means that the above-mentioned coloring opacity of the infrared light absorbent is reduced. Therefore, it can be seen that the coloring opacity of the infrared light absorbent can be adjusted by appropriately selecting the specific surface area and/or the central element M of the phthalocyanine and/or the naphthalocyanine compound.
Any one or plurality of groups of R1 through R8 in the chemical formula (1) and/or (2) may be different from the other groups of R1 through R8.
Compared with the case where the above-mentioned phthalocyanine and/or naphthalocyanine compound has the same R1 through R8, when any one or plurality of groups of R1 through R8 differs, the light-to-heat conversion efficiency can be improved.
The inventors and so forth confirmed that the light-to-heat conversion efficiency tends to increase when the phthalocyanine and/or the naphthalocyanine compound which is formed so that any one or more groups of R1 through R8 may differ from the remaining ones of R1 through R8 in the above-mentioned chemical formula (1) or (2) is used as the infrared light absorbent.
This can be inferred to be because, when the skeleton structure thus differs, the absorption wavelength zone also shifts slightly, and the mixture thereof has a wider light absorption wavelength zone compared with one of a single compound, and thereby it can effectively transform a wider wavelength zone of applied light into heat.
As mentioned above, the infrared light absorbent contained in the toner of the present invention has a light color tone compared with an infrared light absorbent formed of other phthalocyanine and/or naphthalocyanine compound or other compounds, and has an outstanding characteristic that the coloring opacity is small. Therefore, the original color tone of the toner is prevented from being spoiled even for a light color tone, such as lemon yellow.
Furthermore, the toner according to the present invention is such that the amount of addition of the infrared light absorbent to the toner can be reduced necessarily because the reduced amount of addition of the infrared light absorbent can provide the sufficient fixing performance to the toner. This is because the infrared light absorbent having the large heat absorbance per unit weight is used. Also, it is costwisely advantageous, while mitigates the degree of influence thereby given to the toner color tone.
Further, the inventors of the present invention studied on a form of an infrared light absorbent in a toner in an actually usable state. Thereby, the inventors found out a form of a toner for optical fixing such that energy transformation efficiency from light to heat of the toner may improve, while no adverse influence be applied on the hue.
Specifically, according to the thus-obtained knowledge of the inventors, in order to obtain a toner for optical fixing further superior in fixing performance and also in vividness of fixed image, an infrared light absorbent included in a toner should preferably satisfy the following requirements:
A toner for optical fixing, comprises:
a binder resin;
a colorant; and
an infrared light absorbent,
wherein:
not less than 80% in cross-sectional area of particles of the infrared light absorbent in a dispersed state in the toner have Feret circle equivalent diameters falling within a range between 0.05 and 0.5 xcexcm; and
the infrared light absorbent has a structure expressed by the following chemical formula (1) and/or (2); 
wherein:
each of R1 through R8 denotes a substituent added to a benzene ring or a naphthalene ring, and comprises a hydrogen, a halogen atom, a saturated or unsaturated hydrocarbon group having the number of carbons in a range between 1 and 18, or an oxygen and/or nitrogen content hydrocarbon group having the number of carbons in a range between 1 and 13; and
M denotes two hydrogen atoms, a divalent metal, or a trivalent or tetravalent metal derivative.
Thus, the present invention described above has been devised directed to the state of the infrared light absorbent in the toner in a form of a product.
Especially, this form of the present invention exhibits superior performance by adding, in a finely dispersed manner, phthalocyanine and/or naphthalocyanine compounds or so having the above-mentioned chemical formulas (1) and/or (2) as the infrared light absorbent. Further, according to the study by the inventors of the present invention, it is important that more than 80% in cross-sectional area of the particles of the infrared light absorbent in the dispersed state in the toner have Feret circle equivalent diameters falling within the range between 0.05 and 0.5 xcexcm, in order to cause the thus-produced toner to satisfactorily exhibit a superior function of transforming applied optical energy into heat energy.
Further, according to the study by the inventors, in case of manufacture of a toner through grinding, in order to achieve the above-mentioned requirements on the dispersed state of the infrared light absorbent in the toner that more than 80% in cross-sectional area of the particles of the infrared light absorbent in the dispersed state in the toner have the Feret circle equivalent diameters falling within the range between 0.05 and 0.5 xcexcm, it is preferable that the infrared light absorbent be previously ground so fine that the specific surface area of the infrared light absorbent at a time of toner materiel mixing, measured according to the BET manner be not less than 40.0 m2/g, more preferably, on the order of 40.0 through 120.0 m2/g.
For example, in prior to mixing of respective materials of toner, the infrared light absorbent and toner constitutive materials such as binder resin and so forth are mixed for a long time interval by means of a batch-type kneader such as an open-type kneader or the like, so as to apply a considerable amount of kneading stress on the materials. Thereby, the infrared light absorbent are caused to be dispersed finely in the binder resin and so forth, and, thus, the thus-obtained matter may be used as a suitable raw material of the toner.
Further, the inventors of the present invention found out that it is possible to create a form of a toner having a higher light-to-heat transformation efficiency, as the concentration of the infrared light absorbent in the vicinity of the surface of the toner particle can be made higher.
For this purpose, according to the present invention,
a method of manufacturing a toner for optical fixing, which toner comprises:
a binder resin;
a colorant; and
an infrared light absorbent having a structure expressed by the above-mentioned chemical formula (1) and/or (2),
comprises the steps of:
a) dispersing primarily the infrared light absorbent in a non-crosslinked polyester resin serving as a dispersion medium containing diol of not less than 80 mol % of constitutive alcohol; and
b) melting, kneading and grinding the non-crosslinked polyester resin and infrared light absorbent having undergone the step a) with a toner raw material necessarily containing the binder resin, different from the non-crosslinked polyester resin, and the colorant,
wherein the diol is expressed by the following chemical formula (3):
HOxe2x80x94[CR2]nxe2x80x94OHxe2x80x83xe2x80x83Chemical Formula (3)
where:
R denotes hydrogen, methyl group, or ethyl group; and
n denotes a number in a range between 2 and 4, where R is not hydrogen when n=1.
Thereby, it is possible to manufacture a suitable toner for optical fixing.
Further, according to another aspect of the present invention,
a method of manufacturing a toner for optical fixing, which toner comprises:
a binder resin;
a colorant; and
an infrared light absorbent having a structure expressed by the above-mentioned chemical formula (1) and/or (2),
comprises the steps of:
a) dispersing primarily the infrared light absorbent in a wax acting as a dispersion medium which is non-compatible with the binder resin used in the following step b); and
b) melting, kneading and grinding the wax and infrared light absorbent having undergone the step a) with the wax and a toner raw material necessarily containing the binder resin; and the colorant.
Thereby, it is also possible to manufacture a suitable toner for optical fixing.
Further, in the above-described toner manufacture method, it is preferable that the binder resin comprises a polyester resin different from the non-crosslinked polyester resin and also different from the wax, which necessarily includes not less than trivalent acid, and/or not less than trivalent alcohol, and contains at least 1 wt % of insoluble matter for tetrahydroxyfuran.
Further, in the above-described toner manufacture method, it is preferable that the weight concentration of the infrared light absorbent dispersed in the non-crosslinked polyester and/or wax is less than thrice the weight concentration of the infrared light absorbent in the toner; and
a setting is made such that the weight ratio between the non-crosslinked polyester and/or wax and the binder resin in the toner falls in a range between 35:65 and 70:30.
The inventors of the present invention prepared, by using a batch-type kneading machine or the like, non-crosslinked polyester resin containing diol shown by the above-mentioned chemical formula (3) of not less than 80 mol % of the constitutive alcohol and/or wax non-compatible with the binder resin as a dispersion medium. Then, a dispersion process was performed such that this dispersion medium and the infrared light absorbent were kneaded, and thus, the infrared light absorbent was finely dispersed in the dispersion medium. Then, the dispersion medium and infrared light absorbent having undergone the dispersion process were then kneaded with the binder resin, colorant and so forth, and, thus, the toner was obtained in a subsequent preparation process. It was then confirmed that, as the binder resin used there, a resin which necessarily contained not less than trivalent acid and/or not less than trivalent alcohol, and, also, contains not less than 1 wt % of insoluble for tetrahydroxyfuran was used, and, thereby, the light-absorbing-heat-generation amount increased.
In case where a resin is applied as the above-mentioned dispersion medium, the resin can also be regarded as a binder resin. However, the dispersion medium containing the infrared light absorbent in a dispersed state is further contained by another resin in a scattered state, and, thus, the toner is obtained. Accordingly, in order to avoid confusion, the resin used as the dispersion medium (also referred to as a dispersion resin) will not be referred to as a xe2x80x98binderxe2x80x99, while only the other resin which contains the dispersion resin in a scattered state is referred to as a binder resin.
The inventors of the present invention made following consideration as to a reason why the above-mentioned preferable phenomena can be obtained as a result of applying the dispersion medium and binder resin as described above.
(1) The non-crosslinked polyester resin containing diol expressed by the above-mentioned chemical formula (3) of not less than 80 mol % of the constitutive alcohol or a wax is relatively weak and thus has high brittleness against impact.
(2) The resin (binder resin) necessarily containing not less than trivalent acid and/or not less than trivalent alcohol and containing not less than 1 wt % of insoluble for tetrahydroxyfuran is relatively strong and thus has a low brittleness against impact.
(3) Accordingly, when impact is applied to a resin mass of a mixture of the both, there is high probability that the resin mass cleaves at a portion of the dispersion medium (above-mentioned non-crosslinked polyester resin or wax).
(4) Thereby, in case where a toner mass having a form of mixture of the binder resin and the dispersion medium (non-crosslinked polyester resin or wax) is ground, and thus, toner powder is produced, there is a high probability that the above-mentioned non-crosslinked polyester resin or wax is exposed on the surface of the thus-obtained toner powder.
As a result, it is possible to create a form such that the infrared light absorbent primarily dispersed in the dispersion medium (non-crosslinked polyester resin or wax) exists in the vicinity of the toner surface at a high concentration.
(5) In this form of toner, as the infrared light absorbent exists in the vicinity of the toner surface at a high concentration, a probability becomes higher that flash light applied reaches the infrared light absorbent before it is attenuated by the binder resin or the like, and thus, the light-to-heat transformation efficiency improves.
Instead of the above-mentioned non-crosslinked polyester resin, wax or so (dispersion medium) which should previously have the infrared light absorbent dispersed therein, a mixture or a combination of resins, waxes or so having desired properties may be used for the same purpose.
Furthermore, according to an experience of the inventors, it is not preferable to use a high concentration of the infrared light absorbent in the process of kneading and fine dispersion of the infrared light absorbent in the non-crosslinked polyester resin, wax or so. This is because, if the infrared light absorbent was dispersed at a high concentration in the resin, wax or the like used as the dispersion medium, the amount of the resin, wax or the like to be added to the toner would be relatively reduced. Thereby, the above-mentioned probability of cleavage of the resin mass at a portion of the non-crosslinked polyester resin, wax or so at a time of grinding the toner would be reduced, and, also, the infrared light absorbent would be very unevenly distributed in the toner remarkably.
Thus, the toner obtained by the above-described method according to the present invention uses an infrared light absorbent absorbing a large heat amount per unit weight, and, also, the infrared light absorbent is dispersed there at high concentration in the vicinity of the surface thereof. Accordingly, it is possible that the toner has a satisfactory fixing performance with a reduced amount of the infrared light absorbent added thereto. Accordingly, it is possible to control adverse influence of the infrared light absorbent on the hue of an image fixed therethrough, and also, to effectively reduce the costs as the used amount of infrared light absorbent is reduced.
An image forming apparatus according to the present invention performs image formation using the above-mentioned toner for visualizing of a latent image. Thereby, it is possible to obtain color image superior in color tone, fixing performance and image characteristics.